Rolling mill descaling device



.myZ-1970i fcjbikA 3,518,735

RoLLI'nGvuiLL DESCALING DEVICE lFiled July 29. 196e ,-4 sheets-sheet 1 lM V I l INVENTOR.

'BY Tl-OMAQ- c. Daumen-A July 7, 1970 TL QDOMEIKA ROLLING'MILL DESCALING DEVICE Filed July 29. 1968 2 Sheets-Sheet 2 UZK United States Patent O 3,518,736 ROLLING MILL DESCALING DEVICE Thomas C. Domeika, Roanoke, Va., assgnor to General Electric Company, a corporation of New York Filed July 29, 1968, Ser. No. 748,408 Int. Cl. B21c 43/ 04 U.S. Cl. 29-81 4 Claims ABSTRACT OF THE DISCLOSURE Apparatus for assuring uniform descaling of a strip being processed in a hot strip rolling mill wherein water sprays are directed upon the strip uniformly above and below the strip during rolling operations by nozzles carried in frames positioned around the strip between the respective mill stands, the frames being arranged to retain predetermined uniform positions in respect to the strip by position regulators controlled by the looper control mechanism in accordance with strip variations from the rolling line.

BACKGROUND OF THE INVENTION It is common practice in the operation of a so-called hot strip mill, where a red hot bar or slab is passed through a succession of pairs of working rolls, to quench the strip between stands carrying the working rolls. Normally water is sprayed under high pressure upon the top and bottom surfaces of the strip by xed sets of nozzles equally spaced above and below the rolling line not only to reduce strip temperature, but also for removing undesirable scales that form upon the strip surfaces. In the rolling process frequently the strip may deviate vertically from the rolling line either as a result of changes in strip tension, or under influence of the loopers changing position, so that the water sprayed on one surface of the strip is more or less elfective than on the other surface. Uneven cooling may result from this situati-n and scales may not be removed. In some instances the deviation of the strip may cause temperature differences between the top and bottom surfaces of the strip to bring about warping.

SUMMARY OF THE INVENTION The present invention relates to means to prevent irregular cooling and descalding of a metal strip under processing in a hot strip mill by providing variably positioned spraying nozzles under control of the loopers whereby cooling and descalding of both surfaces of the strip remain relatively constant as the strip deviates above and below the rolling line.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a framelike arrangement for carrying nozzles to provide descalding and cooling water sprays in a hot strip mill.

FIGS. 2 is a diagrammatic view of the manner of attaching the framelike structures of FIG. 1 to the hot mill stands, including an illustration of the looper mechanism relationships.

FIG. 3 shows a detailed electrical circuit for providing control from the looper mechanism output to the descaling frame apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. l a descalding unit having a frame 11 in which the horizontal members 12 are provided with a series of nozzles 13 is normally positioned so that a strip of metal being rolled passes within the frame 11 along the line L-M, the frame 11 being attached by arms 17 to a hollow shaft 15 which is rotatable in 3,518,736 Patented July 7, 1970 ICC bearings 21. The hollow shaft 15, the arms 17 and the frame' 11 are constructed of hollow tubing so that a hose 19 connected to one end of the shaft 15 may provide water under pressure to the nozzles 13. The other end of the shaft 15 is plugged to prevent water from escaping and is connected to a gear boX 27 having reduction gearing (not shown) to which a motor shaft 24 is attached, the latter shaft being driven by a motor 23.

Referring now to FIG. 2 there is illustrated the manner in which descalding units 10 are applied to the stands of a hot strip mill. A mill stand 27 having working rolls 31 is provided at its entrance side with a descalding unit 10a, and similarly a stand 28 having working rolls 32 is provided with a descalding unit 10b. Coacting with the rolls of stand 27 is a looper mechanism (not shown, but well understood in the art) including a looper arm 34 pivoted at 34a and provided with a roller 34b which continually contacts the underside of a strip of metal 29 under processing by the strand 27. Similarly, a looper arm 35 pivoted at 35a and having a contacting roller 35b coacting with stand 28 is provided for contacting the strip 29.

The frames 11 of the units 10a and 10b (see FIG. l) are arranged so that they alway are positioned in a plane at right angles to the strip 29, being pivoted in their respective bearings 21 of the stands 27 and 28, respectively, and being rotated in the proper direction by their driving motors 23. With reference momentarily to FIG. 3 a pair of potentiometers LPP and DPP, respectively, are arranged to have their arms rotate in directions corresponding to the directions of rotation of looper arm 34 (or looper arm 35) and frame 11 of descalding unit 10a (or descalding unit 10b). Considering only stand 27, for eX- ample, when looper arm 34 rotates clockwise, its potentiometer arm LPP will rotate in a manner to cause the motor 23 of descalding unit 10a to cause the frame 11 of that unit to be rotated counterclockwise so that the frame 11 positions itself in a plane at right angles to the strip 29'. When his frame 11 rotates its corresponding potentiometer arm DPP also rotates counterclockwise in order to offset the change brought about by the inuence of the looper arm 34 movement, i.e., to bring about a -balanced condition of stability for the frame 11.

While it is obvious that many electrical circuits may be provided to function to cause one mechanical motion in respect to the frame 11 and looper 34 relationship discussed above, the circuit of FIG. 3 has been found to have additional novel features in the circuit embodiment of FIG. 3, which follows:

The circuit of FIG. 3 is essentially a compensated position regulator circuit having an input derived from a potentiometer LPP (which is mechanically controlled from the looper arm 34 of FIG. 2), regulated by way of reference from another potentiometer DPP (which is mechanically controlled by the shaft 15 of FIG. 1, the shaft 15 -being rotated by the motor 23 of FIG. l), and having an output controlling the eld circuit of a direct current generator GEN, which provides current of reversible polarity to a separately excited shunt motor MOT (FIG. 3), which is the same as motor 23 of FIG. l.

The circuit of FIG. 3 may be further broken down into its essential components; i.e., a high gain voltage amplifier PRA, a current amplifier CRA, and a static controlled rectifier bridge SCR which directly provides excitation for the field GF of the generator GEN. (The bridge SCR, being no part of the present invention, accepts the output of the current amplifier CRA both in magnitude and direction and excites the generator eld GF accordingly, thereby controlling the motor MOT.)

The amplifier PRA is actually an error amplifier in respect to the voltage differences between the potential drops of the potentiometers LPP and DPP, which act as voltage dividers across the equal, composite potential sources P50V (positive potential with respect to point X) and N50V (negative potential with respect to point X) when the contacts RI1 and RIZ` are closed, the actual error signal being the algebraic difference between the voltage drops respectively of resistors RPR2 and RPR3 which is fed to the amplifier CRA via a line from point X and a junction point SJ 1. As a result of the potential drop from potentiometer LPP a current flows through resistors RPRZ, RPRI and RCR4 to a junction point SI2 providing the input to the current amplifier CRA. This current is regulated by a voltage compensating circuit, which actually establishes a current reference datum via resistors RPC, IRNC and potentiometers IRHPC, RHNC, together with the diodes CRPC and CRNC between the junction SI1 and the output of amplifier PRA.

By manually adjusting one or the other, or both, of the potentiometers RHPC, RHNC the current reference fed to the current amplier via resistor RCR4 may provide a lead time in the advance or change of rotation of the shaft 15 (FIG. 1) over the reaction time of the looper arm 34 (FIG. 2). This type of control is useful in providing a safety factor in descaling apparatus by keeping the nozzles 13 on the descaling unit away from the hot strip 29 during changes of the strip position in rising above the rolling line, for example.

Similarly when a change in the looper arm occurs as a result of the strip 29 lowering below the rolling line, or from a higher to a lower position, the rotation of the shaft 15 (via motor MOT, i.e., motor 23 of FIG. l) is delayed by time delay circuits, one of which is formed by resistors RPR4 and RPR3 and capacitor CPR1 acting directly upon the amplifier PRA. Another similar time delay circuit is formed by resistors RCR6 and RCRS and capacitor CCR2 acting directly upon the current amplifier via junction SI2, excitation for this circuit being obtained as a current feedback from the generator GEN via an amplistat AS and a shunt SH.

A regulating circuit also may be provided for the current amplifier CRA in the form of a Zener diode Z, and in order t overcome the inherent lagging characteristics of the motor MOT (or motor 23 as in FIG. 1), a further compensating circuit is provided to the current amplifier CRA via junction SI2, this consisting of a network voltage divider per resistors RCRI and RCR2, a capacitor CORI and a limiting resistor RCR3, the latter being connected to the common line A.

Since it is necessary that during the changes of the Work rolls` of any mill stand having a descaling unit according to the present invention the descaling frame 11 (see FIG. 1) be cleared from the rolling line (the looper arm 34 being down normally at such times) an auxiliary contact RC is provided in lieu of contact R11, these contacts being interlocked, the former having a resistor RC1 4 in series so that the reaction of the looper arm 34 is offset to a degree whereby the frame 11 is cleared from the strip 29. Further direct control of the frame 11 is also provided by the jog contacts JF (forward motion) and JR (reverse motion), which are operated manuallyifor purposes of adjustment, these contacts leading from the lines PSV and N50V, respectively, through the resistors RJF and RJR to the junction SI1 of the amplier PRA.

While the invention has been explained and described with the aid of particular embodiments thereof, it will be understood that the invention is not limited thereby and that many modifications retaining and utilizing the spirit thereof without departing essentially therefrom will occur to those skilled in the art in applying the invention to specific operating environments and conditions. It is therefore contemplated by the appended claims to cover all such modifications as fall within the scope and spirit of the invention.

What is claimed is:

1. In a rolling mill having successive stands for processing a length of hot metal, a pivoted arm bearing upon said metal, a descaling device pivotally mounted intermediate said stands including means for delivering coolant to the surfaces of said metal, means for rotating said device under control of a rotation of said arm, and variable electrical means for regulating said rotating means to lead the rotation of said arm.

2. The invention set forth in claim 1 with the further modification of the said variable electrical means for regulating said rotating means to lag the rotation of said arm.

3. The invention of claim 1 wherein the said variable electrical means includes a potentiometer.

4. The invention of claim 1 wherein the said variable electrical means includes a time delay.

References Cited UNITED STATES PATENTS 1,874,080 8/ 1932 Brislin 29-81 2,552,871 5/1951 Shaw 29-81 2,851,042 9/ 1958 Spence 29`81 2,867,893 l/ 1959 Andresen et al. 29-81 2,961,741 11/1960 Cizek 29-81 3,151,197 9/1964 Schultz 29-81 3,378,676 4/ 1968 Clement 118-8 X WALTER A. SCHEEL, Primary Examiner L. G. MACHLIN, Assistant Examiner' U.S. C1. X.R. 

